na-adjective, noun
selfish; self-centered; egotistical
Describes a person or behavior that prioritizes one's own convenience or desires without regard for others. Often used critically.
彼の身勝手な行動に周りは呆れている。
Everyone is fed up with his selfish behavior.
身勝手
It's not good to break a promise for selfish reasons.
Often translated as 'selfish' but leans more toward 'willful' or 'demanding one's own way,' often used for children or spoiled behavior. 身勝手 focuses on disregard for others.
Compound of 身 (oneself) and 勝手 (convenience, one's own way). The exact historical derivation is uncertain, but the combination naturally yields the meaning 'prioritizing one's own convenience.'